Women are disproportionately affected by stroke and many of the strongest risk factors for ischemic stroke in women are associated with altered metabolism. However, exactly how these metabolic alterations directly impact the pathophysiology of stroke is unclear. Metabolomic techniques measure a full profile of small-molecule metabolites, providing a comprehensive picture of an individual's metabolic status. Although preliminary results for cardiovascular disease are promising, no prospective studies for stroke have been conducted. In this application, we propose to evaluate the associations of individual metabolite and metabolomic profiles with subsequent ischemic stroke among women in the Nurses' Health Study I and Nurses' Health Study II, ongoing longitudinal prospective cohort studies. The proposed investigations will use archived fasting blood specimens in concert with detailed behavioral, medical and lifestyle variables. A validated, state-of- the-art metabolomic platform will characterize over 300 metabolites by liquid chromatography tandem mass spectrometry, as well as provide untargeted data. Utilizing a nested case-control design, a two-phase analysis will be conducted with a discovery cohort of 400 stroke cases and their matched controls and a validation cohort of 300 stroke cases/controls to identify and validate novel metabolite and metabolomic profiles associated with incident ischemic stroke in women. Replication in two external cohorts will also be performed. Exploratory analyses will compare the metabolite profiles by subtype of ischemic stroke. Discovery of novel metabolic pathways not previously known to be involved in the pathogenesis of stroke could ultimately lead to new approaches for prevention in the general population and further reduction in morbidity and mortality from stroke.